VMD in principle doesn't care which driver version you use (save for
really old ones), so long as the driver matches the cuda runtime
version. To figure out what is being detected on your machine, run
nvidia-smi. On my computer, which is running Ubuntu 14.04, this is my
output:

The important part is at the top (I've bolded it). Those numbers need to
match, or else nothing cuda-related is going to work. Odds are one of
those two is ahead of or behind the other, which is causing a mismatch
between the cuda runtime (the first number), and the driver version. I
*think* the runtime is hidden in the libcuda package, but I've been
known to misremember things.